Return to cksum.c CVS log

Up to [CSRG BSD Unix] / 43BSD / etc / timed / vax

Annotation of 43BSD/etc/timed/vax/cksum.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1983 Regents of the University of California.
                      3:  * All rights reserved.  The Berkeley software License Agreement
                      4:  * specifies the terms and conditions for redistribution.
                      5:  */
                      6: 
                      7: #ifndef lint
                      8: static char sccsid[] = "@(#)cksum.c    1.2 (Berkeley) 9/18/85";
                      9: #endif not lint
                     10: 
                     11: #include <sys/types.h>
                     12: 
                     13: #define ADD    asm("adwc (r9)+,r8;");
                     14: 
                     15: /* computes the checksum for ip packets for the VAX */
                     16: 
                     17: in_cksum(addr, len)
                     18: u_short *addr;
                     19: int len;
                     20: {
                     21:        register int nleft = len;       /* on vax, (user mode), r11 */
                     22: #ifndef lint
                     23:        register int xxx;               /* on vax, (user mode), r10 */
                     24: #endif not lint
                     25:        register u_short *w = addr;     /* on vax, known to be r9 */
                     26:        register int sum = 0;           /* on vax, known to be r8 */
                     27: 
                     28:        if (((int)w&0x2) && nleft >= 2) {
                     29:                sum += *w++;
                     30:                nleft -= 2;
                     31:        }
                     32:        while ((nleft -= 32) >= 0) {
                     33:                asm("clrl r0");         /* clears carry */
                     34:                ADD; ADD; ADD; ADD; ADD; ADD; ADD; ADD;
                     35:                asm("adwc $0,r8");
                     36:        }
                     37:        nleft += 32;
                     38:        while ((nleft -= 8) >= 0) {
                     39:                asm("clrl r0");
                     40:                ADD; ADD;
                     41:                asm("adwc $0,r8");
                     42:        }
                     43:        nleft += 8;
                     44:        { asm("ashl $-16,r8,r0; addw2 r0,r8");
                     45:          asm("adwc $0,r8; movzwl r8,r8"); }
                     46:        while ((nleft -= 2) >= 0) {
                     47:                asm("movzwl (r9)+,r0; addl2 r0,r8");
                     48:        }
                     49:        if (nleft == -1) {
                     50:                sum += *(u_char *)w;
                     51:        }
                     52: 
                     53:        { asm("ashl $-16,r8,r0; addw2 r0,r8; adwc $0,r8");
                     54:          asm("mcoml r8,r8; movzwl r8,r8"); }
                     55:        return (sum);
                     56: }

This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.